Internet Engineering Task Force (IETF) D. Eastlake 3rd
Request for Comments: 6604 Huawei
Updates: 1035, 2308, 2672 April 2012
Category: Standards Track
ISSN: 2070-1721
xNAME RCODE and Status Bits Clarification
Abstract
The Domain Name System (DNS) has long provided means, such as the
CNAME (Canonical Name), whereby a DNS query can be redirected to a
different name. A DNS response header has an RCODE (Response Code)
field, used for indicating errors, and response status bits. This
document clarifies, in the case of such redirected queries, how the
RCODE and status bits correspond to the initial query cycle (where
the CNAME or the like was detected) and subsequent or final query
cycles.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6604.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Eastlake Standards Track [Page 1]RFC 6604 xNAME RCODE Clarification April 2012Table of Contents
1. Introduction ....................................................2
1.1. Conventions Used in This Document ..........................3
2. Restatement of Status Bits and What They Mean ...................3
2.1. The Authoritative Answer Bit ...............................3
2.2. The Authentic Data Bit .....................................3
3. RCODE Clarification .............................................3
4. Security Considerations .........................................4
5. References ......................................................4
5.1. Normative References .......................................4
5.2. Informative References .....................................5
1. Introduction
The Domain Name System (DNS) has long provided means, such as the
CNAME (Canonical Name [RFC1035]) and DNAME [RFC2672] RRs (Resource
Records), whereby a DNS query can be redirected to a different name.
In particular, CNAME normally causes a query to its owner name to be
redirected, while DNAME normally causes a query to any lower-level
name to be redirected. There has been a proposal for another
redirection RR. In addition, as specified in [RFC2672], redirection
through a DNAME also results in the synthesis of a CNAME RR in the
response. In this document, we will refer to all RRs causing such
redirection as xNAME RRs.
xNAME RRs can be explicitly retrieved by querying for the xNAME type.
When a different type is queried and an xNAME RR is encountered, the
xNAME RR (and possibly a synthesized CNAME) is added to the answer in
the response, DNS Security Extensions (DNSSEC) [RFC4035] RRs
applicable to the xNAME RR may be added to the response, and the
query is restarted with the name to which it was redirected.
An xNAME may redirect a query to a name at which there is another
xNAME and so on. In this document, we use "xNAME chain" to refer to
a series of one or more xNAMEs each of which refers to another xNAME
except the last, which refers to a non-xNAME or results in an error.
A DNS response header has an RCODE (Response Code) field, used for
indicating errors, and status bits that indicate whether an answer is
authoritative and/or authentic. This document clarifies, in the case
of such redirected queries, how the RCODE and status bits correspond
to the initial query cycle (where the (first) xNAME was detected) and
subsequent or final query cycles.
Eastlake Standards Track [Page 2]RFC 6604 xNAME RCODE Clarification April 20121.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",